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1). Weakness in this case is probably due to cortical dysfunction and particularly cortico-spinalneuron dysfunction in the pre-rolandic motor strip. Pressure from the subdural fluid collection canlead to dysfunction of cortical neurons.

2). Inattention is a non-specific finding that can lead to apparent dysfunction of other highercognitive processes. In general, any condition that has a diffuse effect on brain function can lead toinattention. Examples would be drug induced states, metabolic encephalopathies, or increasedintracranial pressure. Depression can also lead to inattentiveness. In this example, the inattentionand confusional episodes may relate to the mass effect of the subdural hematoma. Subduralhematomas are often associated with mental status changes that fluctuate, presumably because offluctuation of intracranial pressure. Increased intracranial pressure leads to a variety of potentialeffects that may cause impaired cognition. These include dysfunction of frontal lobe systems,pressure on the diencephalon with impaired thalamo-cortical interactions, and decreased blood flow.Cerebral blood flow is autoregulated, but when intracranial pressure rises, cerebral blood flow iscompromised. The ultimate level of dysfunction occurs when the intracranial pressure exceeds themean arterial pressure. Then there is no cerebral blood flow and brain death ensues.

3). The brain does not feel pain so that increased intracranial pressure produces headache by othermeans. The dura and the cerebral blood vessels are heavily innervated by nociceptive nerveendings. Pain from increased intracranial pressure is from traction on these pain sensitive structures.Above the tentorium, these fibers are part of C.N. V distribution and pain is often referred to the areainnervated by the ophthalmic division of the trigeminal nerve. The posterior fossa dura and vesselsare innervated by C2-3 and cranial nerves IX and X so pain is referred to the posterior head and neckand occasionally the ear or throat.

4). The subdural space normal holds a thin film of fluid and is a space that can expand whenbridging veins rupture and bleed into the space. The dura is plastered to the periosteum of the skullon one side and the arachnoid on the other. Venous sinuses are formed by the dura and drainbridging veins that pierce the dura. Tearing of these veins is the mechanism of most subduralhematomas. Because the flow pressure in the venous system is low, subdural hematomas may beinsidious in their development and may not be symptomatic for days or weeks after an initial injury.As the hematoma changes in osmotic composition, the hematoma may expand by absorbing CSF.

5). As we get older our brains have some degree of normal atrophy. This creates a largersubarachnoid space and more tension on bridging veins. Some degenerative diseases likeAlzheimers disease are associated with greater than normal cerebral atrophy. Relatively minortrauma can cause subdural hematomas in older people.

Answer to Case History XII

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Figure 1: Two schematic diagrams of the relationship of the dura and subarchnoid space. A:

Relationship between the cortex and meninges showing how the dura forms venous sinuses thatultimately empty into the internal jugular vein. The aracnoid granulations drain CSF into the venoussystem. There are also veins that empty into the dural sinuses. B: Diagram to illustrate the subduraland subarchnoid spaces. The pia mater encompasses vessels as they penetrate the brain. Theepidural space is at the top of the diagram and represents the space between the dura and skull.From Carpenter, M.B. Human Neuroanatomy, 7th edition.

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1). The CT scan showed a mass in the left middle fossa that was extraparenchymal and had aconvex appearance. It was pushing on the left temporal lobe and the left ambient cistern (the CSFspace adjacent to the midbrain) was obliterated. There was also a linear fracture of the left temporalbone. This fracture caused a laceration of the left middle meningeal artery and the formation of anepidural hematoma that formed between the periosteum and the dura. The pressure in the artery ismuch higher than the veins, and the result is a more rapidly expanding mass with significantincreased intracranial pressure. Initially, however, there may be a “lucid interval” with minimalsymptomatology before a mass effect develops.

2). The examination findings are due to compression of the left CN III. The pupillary fibers run onthe outside of the nerve and are most susceptible to pressure. The weakness results fromcorticospinal tract involvement, mostlylikely from cortical compression, butcould also represent the ipsilateralcerebral peduncle being compressed. Thepatient’s obtundation is produced by theincreased intracranial pressure and itstransmission to the diencephalon. Theslow pulse rate and high blood pressure isin response to increased intracranialpressure and is termed Cushing’sresponse. The response tries to maintainmean arterial pressure above intracranialpressure so that cerebral blood flow ispreserved. The caloric responserepresents tonic deviation of the eyestoward the ear irrigated with cold water.There is the loss of the fast phase ofnystagmus in coma. The fast phase ofnystagmus is produced by the frontal eyefields trying to correct the slow deviationof the eyes produced by stimulation of thevestibular apparatus. The loss of left eyeadduction in combination with pupillaryabnormalities is consistent with a lesion ofleft CN III. If the pupil was normal, thecaloric response would be consistent witha lesion of the third nerve nucleus or theleft medial longitudinal fasciculus.

Answer to Case History XIII

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3). As the mass expands, the contralateral cerebral peduncle is compressed against the tentoriumcerebelli causing corticospinal signs and is referred to as the syndrome of Kernohan’s notch. A CNIII palsy with ipsilateral hemiparesis from the cerebral peduncle compression opposite CN III isoften termed a false localizing sign.

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This case demonstrates one of the most distinct forms of aphasia, known as Broca’s aphasia. The caseis taken nearly verbatim from Goodglass & Kaplan (1983).

BROCA’S APHASIA - This condition which often is referred to as nonfluent aphasia. The essentialcharacteristics include: awkward articulation, restricted vocabulary, restriction of grammar to thesimplest, most over-learned forms, and relative preservation of auditory comprehension. Utterancesoften are restricted to short telegraphic phrases consisting of nouns and verbs only, or even to singlewords. Reading is only mildly affected while written language is usually impaired at least as severelyas oral language. Nonspeech oral movements often are affected. Often the individual may haveawareness of the deficit.

Broca’s aphasia arises from a lesion involving the third (inferior) frontal convolution of the lefthemisphere, the subcortical white matter and extending posteriorly to the inferior portion of the motorstrip (precentral gyrus). This condition often is seen with hemiplegia due to involvement of adjacentmotor cortex. (from Goodglass & Kaplan, 1983, pg. 76).

The narrative reveals the typical pattern of compound and complex sentence structures, which getnowhere because semantically meaningless sequences are juxtaposed. Paraphasia consists of totallyirrelevant English words, neologisms, and repetitious overuse of phrases built around the words “time”and “work.”

Answer to Case History XIV

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WERNICKE’S APHASIA - This condition is the most common form of fluent aphasia. The criticalfeatures of this syndrome include impaired auditory comprehension and fluent, easily articulated speech.The speech contains paraphasias. The impairment of auditory comprehension is evident even at theone word level. The individual may repeat the examiner’s words uncomprehendingly, or with paraphasicdistortions. Reading is poor as is writing, although a subgroup may write better than they speak.Paraphasia refers to the production of unintended syllables, words or phrases during efforts to speak.Literal or phonemic paraphasia arises when syllables are produced in the wrong order or when wordsare distorted by inclusion of unintended syllables. “Pipe” may become hike or pike. In the extreme theproduced word may end up a non-word, or neologism (e.g. “Prike”). Verbal or semantic paraphasiaarises when an unintended word is inadvertently used in place of another (e.g. my mother instead of mywife). The individual may have little awareness of the condition. Affected individuals usually appearcontent, happy, and sometimes even jocular. They typically appear to make light of their problem, andexpress little or no frustration.

Hemiparesis is unlikely, because the lesion is in the posterior portion of the superior temporal gyrus ofthe left hemisphere.

Answer to Case History XV

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A.M. had a vascular accident diagnosed as a thrombosis in the distribution of the left middle cerebralartery, with effects extending posteriorly to the angular gyrus.

Clinical Characteristics of Cortical Aphasias(these will be discussed by your instructor in more detail)

+ good/present- poor/absentRHP = right hemiparesisRHH = right homonymous hemianopsia

Goodglass, H., & Kaplan, E. (1983). The assessment of aphasia and related disorders (2nd ed.).Philadelphia, PA: Lea & Febiger.

Type Verbal Output

Compre-hension

Repetition Naming Associated Signs

Lesion Site

Broca's nonfluent + - +/- RHP 3rd frontal gyrus

Wernicke's fluent - - - RHH superior temporal

gyrus

Global nonfluent - - - RHH

Anomic fluent + + -

Conduction fluent + - - arcuate fasciculus

Transcortical Motor

nonfluent + + -

Transcortical Sensory

fluent - + -

Mixed nonfluent - + -

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A 34-year-old woman comes to see you because of problems with her balance and walking. She hasnoticed this for the past few days and her symptoms do not appear to be getting better. In addition,she feels numbness and tingling in her hands and feet. Sometimes when she bends her head forwardshe may feel an electrical shock going down the spine. When she is out in the summer heat, hersymptoms seem to get worse and she may develop double vision. About 12 years ago she lost visionin her right eye. This recovered with treatment. She had some double vision in the past but notrecently except when she was out in the heat. There is no family history of neurological problems.

On exam you find her mental status is normal. Cranial nerves exam was remarkable for a rightafferent papillary defect (light in the left eye caused constriction but moving the light to the right eyeresulted in both pupils to dilate) and visual acuity in the right eye was 20/30 even with correction.When looking to the left there was nystagmus in the left eye and the patient complained of doublevision with looking to the left, but not to the right. A right eye adductor weakness was present onlateral gaze but not convergence. The rest of the cranial nerves were normal. Motor exam showedgood strength in the upper extremities proximally but mild right grip weakness. Reflexes in theupper extremity were normal. In the lower extremities there was mild weakness bilaterally withsome focal weakness in right foot dorsiflexion. Tone seemed increased in the legs, reflexes werebrisk, and a definite right Babinski sign was present. Sensory exam was normal to pin prick butthere was a decrease in vibration and proprioception in the toes and fingers. Vibration sensationchanges on the cervical vertebral bodies around C4-5. Cerebellar function was okay on finger-nose-finger testing, although rapid alternating movements in her right hand were clumsy. Heel to shintesting was performed slowly but accurately. Her gait was unsteady and wide-based. She couldstand with her feet together but tended to fall with her eyes closed.

1. Explain the deficits on neurological exam. Where and how many lesions can explain thiswoman’s findings?

Answer:

Lesion 1: Cranial nerve II on the right, afferent papillary defect and change in vision in one eyepoints to a lesion anterior to the chiasm in the optic nerve. The afferent papillary defect points to adecrease in light recognition in the right eye. The efferent part of the papillary reflex mediated bythe third nerve is intact as observed by the convergence. Visual acuity is also affected.

Lesion 2: Right medial longitudinal fasiculus lesions produce a right internuclear ophthalmoplegia.This resulted in lack of yoking of the left VI motor neurons and right III motor neurons to theinnervate the right medial rectus muscle of the eye. Convergence is intact because this pathway isgenerated from midbrain neurons not from the left PPRF (para pontine reticular formation) thatsends connections to the contralateral III n nucleus via the medial longitudinal fasiculus.

Lesion 3: There appears to be mild right-sided weakness that had characteristics of upper motorneuron lesions (increased reflex and Babinski sign). A lesion anywhere in the corticospinal tractcould produce this. The increased reflexes in the legs point to the possibility there may also be alesion in the corticospinal tract. Subcortical white matter lesions can cause hemiparesis.

Answer to Case History XVI

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Lesion 4: There is bilateral loss of vibration and position sense in the all four extremities with anapparent level at C4-5. Positive Lhermitte’s sign is suggested by the history. Positive Romberg test(loses balance with eyes closed) points to a problem with either the vestibular system orproprioceptive system. These findings point to cervical dorsal column involvement.

What could cause this clinical picture and what tests would you perform?

This clinical picture is consistent with multiple lesions in the central nervous system that occurred atdifferent times. This picture may be seen for a variety of reasons but most commonly occurs withmultiple sclerosis when the optic nerve and medial longitudinal fasiculus are involved. Vasculitismay also produce multiple small lesions and would need to be considered.

We would image to define where the lesions are and in this case would consider a head and cervicalspine MRI scan. In multiple sclerosis periventricular lesions of the white matter are observed.Some active change in the blood barrier may be observed if gadolinium contrast is used. Activeinvolvement of the immune system may be demonstrated by abnormal CSF findings of increasedprotein level and the presence of a modest number of lymphocytes (10-100/cc). A relative increasein the IgG component of the protein content present and associated with oligoclonal bands of IgG.

2. Why does she have more problems in the heat?

Multiple sclerosis is characterized by a loss of central myelin with associated inflammatory changes.Demyelination can cause conduction block and loss of function, particularly at warmer temperatureswhen the sodium action potential shortens in duration and conduction failure of propagating actionmay be more likely to occur.

3. What treatment did she receive 12 years ago and what treatments should be considered?

The patient’s original symptoms of loss of vision in the right eye probably relate an episode of opticneuritis. Optic neuritis may be treated acutely with steroid drugs that decrease inflammation. Flair-ups or exacerbation of multiple sclerosis symptoms may also be treated acutely with steroids. Sometreatments are directed at preventing attacks by altering the immune system (beta-interferon or ainjection with a polymer that has similarity to myelin basic protein). In some cases more robustimmunosupression is used including cancer chemotherapeutic agents.

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A 70-year-old man presents with diplopia and right eye and forehead pain. He first noted troublesabout 6 months ago. At first his complaints were intermittent but now they are present nearly all thetime. His past medical history is pertinent for hypertension and colon cancer, treated surgically 5years ago. He was involved in a car accident about 2 years ago that was associated with loss ofconsciousness but not hospitalization. A CT scan in the ER was normal.

On exam: his mini-mental status was 27/30 (losing points for memory 1, county 1, figure 1).Cranial nerves: right pupil larger than the left by 2 mm and light reflex less brisk than the left pupil.Fundoscopic exam negative. Visual acuity and fields normal. Mild right ptosis was noted. Fullextraocular movements were obtained but the patient complains of double vision when looking tothe left either downward or upward with images vertically displaced, more horizontally displacedwith direct left lateral gaze. Mild decrease sensation first division of V cranial nerve. Otherwisecranial nerves normal. Motor and sensory exam remarkable for a decrease in ankle jerks andvibration bilaterally. Gait normal for age.

1. Where is the lesion?

There is involvement of the right III n (ptosis and larger pupil with weakness of the medial rectusand inferior oblique). A right IV may also be present because the trouble of vision down and to theleft. If the IV n is affected, there should also be loss of intorsion when the affected eye is tested tolook downward. Also loss of sensation in the forehead suggests the first division of V is involved.These nerves all are close to the superior orbital fissure and travel in the lining of cavernous sinus.

The decrease in reflexes at the ankle and decreased vibration in the feet are common findings in theelderly and probably are unrelated to his current symptoms. They may represent a mild peripheralneuropathy and if macrocytosis was present on his blood smear, B12 and folate levels should bechecked.

2. What could cause the lesion?

A small meningioma (tumor of the meninges) could cause these deficits at the superior orbital fissureor an aneurysm of the internal carotid artery. Invasive tumors from the sphenoid sinus or sellatursica can invade the walls of the cavernous sinus and affect II, III, IV, VI, and V 1 or 2 cranialnerves. In some cases trauma as occurred in this man could produce a fistula formation betweenthe internal carotid artery and the cavernous sinus. In these cases proptosis of the eye may occur anda bruit may be present. The etiology can be defined by imaging studies (MRI, MRA, angiogram).

Answer to Case History XVII

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